Mechanism for bipolar resistive switching in transition metal oxides

We introduce a model that accounts for the bipolar resistive switching phenomenom observed in transition metal oxides. It qualitatively describes the electric field-enhanced migration of oxygen vacancies at the nano-scale. The numerical study of the model predicts that strong electric fields develop in the highly resistive dielectric-electrode interfaces, leading to a spatially inhomogeneous oxygen vacancies distribution and a concomitant resistive switching effect. The theoretical results qualitatively reproduce non-trivial resistance hysteresis experiments that we also report, providing key validation to our model.Comment: Accepted for publication in Physical Review B, 6 twocolumn pages, 5 figure

L1CAM binds ErbB receptors through Ig-like domains coupling cell adhesion and neuregulin signalling.

During nervous system development different cell-to-cell communication mechanisms operate in parallel guiding migrating neurons and growing axons to generate complex arrays of neural circuits. How such a system works in coordination is not well understood. Cross-regulatory interactions between different signalling pathways and redundancy between them can increase precision and fidelity of guidance systems. Immunoglobulin superfamily proteins of the NCAM and L1 families couple specific substrate recognition and cell adhesion with the activation of receptor tyrosine kinases. Thus it has been shown that L1CAM-mediated cell adhesion promotes the activation of the EGFR (erbB1) from Drosophila to humans. Here we explore the specificity of the molecular interaction between L1CAM and the erbB receptor family. We show that L1CAM binds physically erbB receptors in both heterologous systems and the mammalian developing brain. Different Ig-like domains located in the extracellular part of L1CAM can support this interaction. Interestingly, binding of L1CAM to erbB enhances its response to neuregulins. During development this may synergize with the activation of erbB receptors through L1CAM homophilic interactions, conferring diffusible neuregulins specificity for cells or axons that interact with the substrate through L1CAM

Yearly evolution of organ damage markers in diabetes or metabolic syndrome: data from the LOD-DIABETES study

<p>Abstract</p> <p>Background</p> <p>Cardiovascular disease morbidity-mortality is greater in people with type 2 diabetes mellitus or metabolic syndrome. The purpose of this study was to evaluate the yearly evolution of organ damage markers in diabetes or metabolic syndrome, and to analyze the associated factors.</p> <p>Methods</p> <p>An observational prospective study was carried out in the primary care setting, involving 112 patients: 68 diabetics and 44 subjects with metabolic syndrome, subjected to 12 months of follow-up. Measurements: traditional cardiovascular risk factors (blood pressure, blood glucose, lipids, smoking, body mass index (BMI) and) and non-traditional risk factors (waist circumference, hsC Reactive Protein and fibrinogen); subclinical vascular (carotid intima-media thickness, pulse wave velocity and ankle/brachial index), cardiac (Cornell voltage-duration product), renal organ damage (creatinine, glomerular filtration and albumin/creatinine index), and antihypertensive and lipid-lowering drugs.</p> <p>Results</p> <p>At baseline, the diabetics presented a mean age of 59.9 years, versus 55.2 years in the subjects with metabolic syndrome (p = 0.03). Diastolic blood pressure, total cholesterol and HDL-cholesterol were lower among the patients with diabetes, while blood glucose and HbA1c, as well as antihypertensive and lipid-lowering drug use, were greater. At evaluation after one year, the diabetics showed a decrease in BMI (-0.39), diastolic blood pressure (-3.59), and an increase in fibrinogen (30.23 mg/dL), ankle/brachial index (0.07) and the number of patients with ankle/brachial index pathologic decreased in 6. In turn, the patients with metabolic syndrome showed an increase in HDL-cholesterol (1-91 mg/dL), fibrinogen (25.54 mg/dL), Cornell voltage-duration product (184.22 mm/ms), ankle/brachial index (0.05) and the use of antihypertensive and lipid-lowering drugs, and a reduction in serum glucose (3.74 mg/dL), HOMA, systolic (-6.76 mmHg), diastolic blood pressure (-3.29 mmHg), and pulse wave velocity (-0.72 m/s). The variable that best predicted a decrease in pulse wave velocity in subjects with metabolic syndrome was seen to be an increase in antihypertensive drug use.</p> <p>Conclusions</p> <p>The annual assessment of cardiovascular risk factors and the decrease in pulse wave velocity was more favorable in the patients with metabolic syndrome, probably influenced by the increased percentage of subjects treated with antihypertensive and lipid lowering drugs in this group.</p

Preliminary optical design of PANIC, a wide-field infrared camera for CAHA

In this paper, we present the preliminary optical design of PANIC (PAnoramic Near Infrared camera for Calar Alto), a wide-field infrared imager for the Calar Alto 2.2 m telescope. The camera optical design is a folded single optical train that images the sky onto the focal plane with a plate scale of 0.45 arcsec per 18 micron pixel. A mosaic of four Hawaii 2RG of 2k x 2k made by Teledyne is used as detector and will give a field of view of 31.9 arcmin x 31.9 arcmin. This cryogenic instrument has been optimized for the Y, J, H and K bands. Special care has been taken in the selection of the standard IR materials used for the optics in order to maximize the instrument throughput and to include the z band. The main challenges of this design are: to produce a well defined internal pupil which allows reducing the thermal background by a cryogenic pupil stop; the correction of off-axis aberrations due to the large field available; the correction of chromatic aberration because of the wide spectral coverage; and the capability of introduction of narrow band filters (~1%) in the system minimizing the degradation in the filter passband without a collimated stage in the camera. We show the optomechanical error budget and compensation strategy that allows our as built design to met the performances from an optical point of view. Finally, we demonstrate the flexibility of the design showing the performances of PANIC at the CAHA 3.5m telescope.Comment: This paper has been presented in the SPIE of Astronomical Telescopes and Instrumentation 2008 in Marseille (France

On Doppler tracking in cosmological spacetimes

We give a rigorous derivation of the general-relativistic formula for the two-way Doppler tracking of a spacecraft in Friedmann-Lemaitre-Robertson-Walker and in McVittie spacetimes. The leading order corrections of the so-determined acceleration to the Newtonian acceleration are due to special-relativistic effects and cosmological expansion. The latter, although linear in the Hubble constant, is negligible in typical applications within the Solar System.Comment: 10 pages, 1 figure. Journal versio

Synthesis of quinoxaline 1,4-di-N-oxide derivatives on solid support using room temperature and microwave-assisted solvent-free procedures

We describe the synthesis of 12 new ethyl and methyl quinoxaline-7-carboxylate 1,4-di-N-oxide derivatives on solid supports with room temperature and microwave-assisted solvent-free procedures. Results show that solid supports have good catalytic activity in the formation of quinoxaline 1,4-di-N-oxide derivatives. We found that florisil and montmorillonite KSF and K10 could be used as new, easily available, inexpensive alternatives of catalysts. Additionally, room temperature and microwave-irradiation solvent-free synthesis was more efficient than a conventional procedure (Beirut reaction), reducing reaction time and increasing yield

Harnessing Student Leadership in Building a Center for Students in Recovery at a Private Catholic University in Central Texas

This presentation describes the different processes and steps taken by two faculty members from the social work department and a group of students to start a Center for Student Recovery (CSR) at a small private university in central Texas serving mostly first-generation Hispanic students. The presentation highlights the unique history of the university and how its mission and values align with the creation of a CSR, making it the first private catholic university with this type of service to its student population.&nbsp; Additionally, the presentation showcases the different stages undergone by the stakeholders to get to the point of student involvement.&nbsp; The stages include the social work department obtaining part of an SBIRT (Screening, Brief Intervention, and Referral to Treatment) grant which allowed for training to be embedded in certain classes which sparked conversations of substance and alcohol use among the student population. It also included a student health survey that provided a snapshot of the state of substance and alcohol use on campus, and the approval of a proposal presented to the University’s board of trustee and president. Emphasis is given to the process of recruiting the student leadership, the student’s motivation and their role in the creation of the CSR

Transient study of the oxygen reduction reaction on reduced Pt and Pt alloys microelectrodes: evidence for the reduction of pre-adsorbed oxygen species linked to dissolved oxygen

Using chronoamperometry at preconditioned oxide-free Pt microdisc electrodes in aqueous media, we investigated the oxygen reduction reaction (ORR) on the millisecond timescale and obtained results consistent with the reduction of oxygen species which adsorb on the electrode before the ORR is electrochemically driven. Furthermore these adsorbed species are clearly linked to oxygen in solution. At long times, the amperometric response is solely controlled by the diffusion of dissolved oxygen towards the microelectrode. However, at short times, typically below 50 ms, the reduction of pre-adsorbed oxygen produces a large extra current whose magnitude depends on the oxygen concentration in solution, deliberate electrode poisoning and the rest time before the potential step. Using sampled current voltammetry we show that this extra current affects the entire potential range of the ORR. Using microdisc electrodes made with Pt alloys we find that the amperometric response is sufficiently sensitive to distinguish oxygen coverage differences between Pt, Pt0.9Rh0.1 and Pt0.9Ir0.1 microdiscs. These unexpected and, to our knowledge, never previously reported results provide new insight into the oxygen reduction reaction on Pt. The existence over a wide potential range of irreversibly adsorbed oxygen species arising from dissolved oxygen and different from Pt oxide is particularly relevant to the development of oxygen reduction catalysts for low temperature fuel cells

After Nerve Injury, Lineage Tracing Shows That Myelin and Remak Schwann Cells Elongate Extensively and Branch to Form Repair Schwann Cells, Which Shorten Radically on Remyelination

There is consensus that, distal to peripheral nerve injury, myelin and Remak cells reorganize to form cellular columns, Bungner's bands, which are indispensable for regeneration. However, knowledge of the structure of these regeneration tracks has not advanced for decades and the structure of the cells that form them, denervated or repair Schwann cells, remains obscure. Furthermore, the origin of these cells from myelin and Remak cells and their ability to give rise to myelin cells after regeneration has not been demonstrated directly, although these conversions are believed to be central to nerve repair. Using genetic lineage-tracing and scanning-block face electron microscopy, we show that injury of sciatic nerves from mice of either sex triggers extensive and unexpected Schwann cell elongation and branching to form long, parallel processes. Repair cells are 2- to 3-fold longer than myelin and Remak cells and 7- to 10-fold longer than immature Schwann cells. Remarkably, when repair cells transit back to myelinating cells, they shorten ∼7-fold to generate the typically short internodes of regenerated nerves. The present experiments define novel morphological transitions in injured nerves and show that repair Schwann cells have a cell-type-specific structure that differentiates them from other cells in the Schwann cell lineage. They also provide the first direct evidence using genetic lineage tracing for two basic assumptions in Schwann cell biology: that myelin and Remak cells generate the elongated cells that build Bungner bands in injured nerves and that such cells can transform to myelin cells after regeneration